Apparatus and method for controlling a compressor

ABSTRACT

An apparatus and method for controlling a compressor are provided. An input voltage of a commercial power source, a motor voltage of a compressor motor, and a motor current of the compressor motor are detected, based on which voltage values of a capacitor and voltage values of a triac may be calculated. Thus, an additional operational amplifier or a sensor to measure a capacitor voltage is not required, reducing costs.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Pursuant to 35 U.S.C. §119(a), this application priority to Korean Application No. 10-2012-0009078, filed on Jan. 30, 2012, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND

1. Field

An apparatus for controlling a compressor and a method for controlling a compressor are disclosed herein.

2. Background

Apparatuses and methods for controlling a compressor are known. However, they suffer from various disadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:

FIG. 1 is a graph showing capacitor voltage calculation values of a capacitor of an apparatus for controlling a compressor according to an embodiment;

FIG. 2 is a graph showing triac voltage calculation values of a triac of the apparatus for controlling a compressor according to an embodiment;

FIG. 3 is a schematic diagram of an apparatus for controlling a compressor according to an embodiment;

FIG. 4 is a flow chart of a method for controlling a compressor according to an embodiment;

FIG. 5 is a cross-sectional view of a reciprocating compressor included in an apparatus for controlling a compressor according to embodiments; and

FIG. 6 is a perspective view of a refrigerator employing the reciprocating compressor of FIG. 5.

DETAILED DESCRIPTION

Description will now be given in detail of embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated.

In general, a compressor, a device that converts mechanical energy into compression energy, may be used as part of refrigeration equipment, for example, a refrigerator, or an air-conditioner. A compressor may be classified as a reciprocating compressor, a rotary compressor, or a scroll compressor. In the reciprocating compressor, a compression space, into or from which an operating gas is sucked or discharged, is formed between a piston and a cylinder, and a piston linearly reciprocates within a cylinder to compressor a refrigerant. In the rotary compressor, a compression space, into or from which an operating gas is sucked or discharged, is formed between an eccentrically rotating roller and a cylinder, and the roller eccentrically rotates along an inner wall of the cylinder to compress a refrigerant. In the scroll compressor, a compression space, into or from which an operating gas is sucked or discharged, is formed between an orbiting scroll and a fixed scroll, and the orbiting scroll rotates along the fixed scroll to compress a refrigerant.

In general, a reciprocating compressor, in which a piston linear reciprocates within a cylinder to suck, compress, and discharge a refrigerant gas, is classified as a recipro compressor and a linear compressor according to a method of driving a piston. The recipro compressor is a reciprocating compressor, in which a crank shaft is coupled to a rotary motor and a piston is coupled to the crank shaft to change rotatory power of the rotary motor into a linear reciprocal movement. The linear compressor is a reciprocating compressor, in which a piston is directly connected to a mover of a linear motor to reciprocate a piston by a linear motion of the motor.

As described above, the linear compressor does not employ a crank shaft to convert a rotational motion to a linear motion, causing less frictional loss, so its performance is excellent relative to a general compressor in terms of compression efficiency. The linear compressor may be used in a refrigerator or an air-conditioner, to vary a voltage applied to a compressor to control freezing capacity.

In the linear compressor, in order to improve a usage rate of an applied voltage, an AC capacitor may be connected in series to configure an apparatus for controlling a compressor. Also, the apparatus for controlling a compressor generally detects a motor voltage and a motor current of a compressor motor, calculates a stroke, and controls a compressor based on the stroke. However, in the apparatus for controlling a compressor, in order to protect a compressor against, for example, an overload in controlling the compressor, voltage values of a capacitor and a triac connected to the compressor should be continuously or periodically detected. However, additional installation of a new operational amplifier (OPAMP) in order to continuously or periodically detect the voltage values increases costs. An apparatus for controlling a compressor according to an embodiment may include one or more capacitors connected to a compressor motor, a triac that operates the compressor motor according to a gate driving signal, and a microcomputer that generates the gate driving signal, and calculates voltage values of the capacitors and the triac using values of an input voltage of a commercial power source, a motor voltage of the compressor motor, and a motor current of the compressor motor.

Hereinafter, an apparatus for controlling a compressor and a method for controlling a compressor according to embodiments will be described in detail with reference to the accompanying drawings.

First, a reciprocating compressor applied to embodiments will be described in detail with reference to FIG. 5. The reciprocating compressor 100 of FIG. 5 may include a casing 800, to which a gas suction pipe SP and a gas discharge pipe DP may be connected, a frame 200 elastically supported within the casing 800, a motor 300 supported by the frame 200 and having a mover 330 that linearly reciprocates, a compression device 400 having a piston 420 coupled to the mover 330 of the motor 300 and supported by the frame 200, and a plurality of resonance devices 500 that elastically supports the mover 330 of the motor 300 and the piston 420 of the compression device 400 in a motion direction to induce a resonant movement.

The frame 200 may include a first frame 210 that supports the compression device 400 and a front side of the motor 300, a second frame 220 coupled to the first frame 210 that supports a rear side of the motor 300, and a third frame 230 coupled to the second frame 220 that supports a plurality of second resonance springs 530. The first frame 210, the second frame 220, and the third frame 230 may be made of a non-magnetic material, such as aluminum, to reduce iron loss.

The first frame 210 may include a frame part 211 formed to have an annular plate shape, and a cylinder part 212 having a cylindrical shape integrally formed to extend to a rear side, namely, toward the motor, such that a cylinder 410 may be inserted at a center of the frame part 211. The frame part 211 may be formed such that an outer diameter thereof is not at least smaller than an inner diameter of an outer stator 310 of the motor 300 in order to support both the outer stator 310 and an inner stator 320 of the motor 300.

The inner stator 320 may be insertedly fixed to an outer circumferential surface of the cylinder part 212. The first frame 210 may be made of a non-magnetic material, such as aluminum, to prevent a loss of magnetic force. The cylinder part 212 may be integrally formed in the cylinder 410 by, for example, an insert-dicasting technique. However, the cylinder 410 may be press-fit to an inner circumferential surface of the cylinder part 212, or the inner circumferential surface of the cylinder part 212 may be threaded to screw-assemble the cylinder 410. The cylinder part 212 may have a step surface or a sloped surface between a front inner circumferential surface and a rear inner circumferential surface to allow the cylinder 410 coupled to the inner circumferential surface of the cylinder part 212 to be supported in the direction of the piston, and this may be advantageous in terms of stability of the cylinder 410.

The motor 300 may include the outer stator 310, which may be supported between the first frame 210 and the second frame 220 and have a coil 311 wound therearound, the inner stator 320 coupled to an inner side of the outer stator 310 with a certain gap therebetween and insertedly positioned on the cylinder part 212, and a mover 330 including a magnet 331 corresponding to the coil 311 of the outer stator 310 and making a linear reciprocal movement in a magnetic flux direction between the outer stator 310 and the inner stator 320. The outer stator 310 and the inner stator 320 may be formed, for example, by laminating a plurality of sheets of thin stator cores to have a cylindrical shape or by laminating a plurality of sheets of thin stator cores to have a block shape and radially laminating the stator blocks.

The compression device 400 may include the cylinder 410, which may be integrally formed with the first frame 210, the piston 420 coupled to the mover 330 of the motor 300 that makes a reciprocal movement in a compression space P of the cylinder 410, a suction valve 430 installed on a front end of the piston 420 that adjusts suction of a refrigerant gas by opening and closing a suction flow path 421 of the piston 420, a discharge valve 440 installed at a discharge side of the cylinder 410 that adjusts discharging of a compression gas by opening and closing the compression space P of the cylinder 410, a valve spring 450 that elastically supports the discharge valve 440, and a discharge cover 460 fixed to the first frame 210 at the discharge side of the cylinder 410 such that the discharge valve 440 and the valve spring 450 are accommodated.

The cylinder 410 may have a cylindrical shape and be insertedly coupled to the cylinder part 212 of the first frame 210. The cylinder 410 may form a bearing surface with the piston 420 having an inner circumferential surface made of, for example, cast iron, and in order to avoid abrasion of the cylinder 410 by the piston 420, the cylinder 410 may be made of a material having a higher hardness than that of the first frame 210, more specifically, the cylinder part 212.

The piston 420 may be made of the same material as that of the cylinder 410 or may be made of a material having a hardness which is at least similar to that of the cylinder 410 to reduce abrasion with the cylinder 410. The suction flow path 421 may be formed to penetrate an interior of the piston 420 to allow a refrigerant to be sucked into the compression chamber P of the cylinder 410.

The resonance device 500 may include a spring supporter 510 coupled to a connection portion of the mover 330 and the piston 420, first resonance springs 520 supported by a front side of the spring supporter 510, and second resonance springs 530 supported by a rear side of the spring supporter 510.

Reference numeral 422 denotes a piston connection portion and reference numeral 600 denotes an oil feeder.

When power is applied to the motor 300 and magnetic flux is formed between the outer stator 310 and the inner stator 320, the mover 330 placed in an air gap between the outer stator 310 and the inner stator 320 may move in a direction of the magnetic flux and continuously makes a reciprocal movement by the resonance device 500. When the piston 420 makes a backward movement within the cylinder 410, a refrigerant filled in the internal space of the casing 800 may be sucked into the compression space P of the cylinder 410 through the suction flow path 421 of the piston 420 and the suction valve 430. When the piston 420 makes a forward movement within the cylinder 410, the refrigerant gas sucked into the compression space P may be compressed and open the discharge valve 440 so as to be discharged. This sequential process may be repeatedly performed.

The reciprocating compressor according to embodiments may include an apparatus for controlling a compressor as follows. Also, the reciprocating compressor may be used in refrigeration equipment, such as a refrigerator or an air-conditioner. For example, referring to FIG. 6, in a refrigeration equipment 700 having a refrigerant compression type refrigerating cycle including a compressor, a condenser, an expander, and an evaporator, a main board 710 that controls a general operation of the refrigeration equipment 700 may be provided and the reciprocating compressor C may be connected to the main board 710. The apparatus for controlling a compressor may be provided in the main board 710.

Hereinafter, an apparatus for controlling a compressor, which may include the reciprocating compressor 100 as described above, according to embodiments, will be described in detail with reference to FIG. 3. As illustrated, the apparatus for controlling a compressor may include a commercial power source 10, a triac 20, a compressor 30 (100), an alternating current (AC) capacitor 40, and a microcomputer 90. The apparatus for controlling a compressor may further include an input voltage detector 50, a motor voltage detector 60, a zero voltage detector 70, and a motor current detector 80. However, such a configuration may vary as necessary.

The commercial power source 10 may supply power to the compressor 30. Upon receiving power from the commercial power source 10, the compressor 30 may perform a reciprocal movement of a piston. The commercial power 10 may be, for example, AC power of 220V which is generally used in households.

The triac 20 may operate the motor of the compressor 30 according to a gate driving signal. In more detail, the triac 20 may be connected in series to the compressor 30 and operate the compressor 30 according to a gate driving signal received from the microcomputer 90. In one embodiment, in preparation for a malfunction due to abnormal driving, the triac 20 may include a switch, for example, a triac protection relay (not shown), that protects the triac 20.

The capacitor 40 may be connected to a motor of the compressor 30, and may have a capacitance corresponding to an inductance of a coil wound around the motor of the compressor 30. As the capacitor 40, an AC capacitor may be used; however, embodiments are not limited thereto.

The microcomputer 90 may calculate voltage values of the capacitor 40 and the triac 20 using values of an input voltage of the commercial power source 10, a motor voltage of the motor of the compressor 30, and a motor current of the motor of the compressor 30. Also, the microcomputer 90 may generate a gate driving signal for controlling ON/OFF of the triac 20.

The microcomputer 90 may include a capacitor voltage calculator 92 that calculates voltage values of the capacitor 40 and a triac voltage calculator 94 that calculates voltage values of the triac 20. Thus, the apparatus for controlling a compressor according to an embodiment does not need to include an extra sensor or an additional operational amplifier (OPAMP) to detect the voltage of the capacitor 40 and the voltage of the triac 20.

First, relationships among the input voltage, the motor voltage, the capacitor voltage, and the triac voltage may be represented by Equation 1 below from a general motor equation.

$\begin{matrix} {{V_{m} = {{Ri}_{m} + {L\frac{i_{m}}{t}} + {K\frac{x}{t}}}}{{V_{i\; n} = {V_{m} + V_{cap} + V_{triac}}},\left( {{V_{cap}} = {\frac{1}{C}{\int{i_{m}{t}}}}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$

Here, Vin is an input voltage of the commercial power source, Vm is a motor voltage, Vcap is a voltage of the capacitor, and Vtriac is a voltage of the triac. Also, i is a motor current flowing in the compressor motor, R is internal resistance of the compressor, L is inductance of a motor coil, K is a motor constant, and C is capacitance forming a resonance circuit together with L.

When the value of the motor current flowing in the compressor motor is 0, the capacitor voltage calculator 92 may calculate a predetermined value as a capacitor voltage value. Namely, in a section of a motor current waveform in which the motor current value is 0, there is no change in the capacitor voltage value. Thus, in the section of the motor current waveform in which the motor current value is 0, there is no change in the capacitor voltage value. Also, when the value of the motor current flowing in the compressor motor is not 0, the capacitor voltage calculator 92 may calculate a value obtained by subtracting the motor voltage from the input voltage, as a capacitor voltage value.

A graph including capacitor voltage values calculated by the capacitor voltage calculator 92 is illustrated in FIG. 1. As illustrated in FIG. 1, waveforms of the input voltage, the motor voltage, and the motor current detected through one or more sensors are illustrated. The capacitor voltage values are derived using the detected input voltage, motor voltage, and the motor current values. The capacitor voltage value may be derived from Equation 1 as follows.

Vcap(k)=Vin(k)−Vm(k)−Vtriac(k)

Equation 2 below may be derived using the fact that when the value of the current flowing in the motor of the compressor 30 is not 0, the voltage of the triac 20 is 0.

V cap(k)=Vin(k)−Vm(k)  [Equation 2]

Also, Equation 3 below may be derived using the fact that when the current value flowing in the motor of the compressor 30 is not 0, there is no change in the voltage of the capacitor 40.

V cap(k)=Vcap(k−1)  [Equation 3]

Referring to FIG. 1, as the current value flowing in the motor of the compressor 30 in a first region illustrated in FIG. 1 is not 0, a capacitor voltage value is calculated by Equation 2. Namely, in this case, a result value obtained by subtracting a voltage value applied to the motor of the compressor 30 from the input voltage value of the commercial power source 10 is calculated as a capacitor voltage value.

Also, as the current value flowing in the motor of the compressor 30 in a second region shown in FIG. 1 is 0, a capacitor voltage value is calculated by Equation 3. Namely, in this section, there is no change in the capacitor voltage value in the second section and a predetermined value is calculated as a capacitor voltage value.

The current value flowing in the motor of the compressor 30 may be 0 during a predetermined region or at a particular vertex. In any event, the capacitor voltage value is calculated by Equation 3. For example, when the motor current value flowing in the motor of the compressor 30 during the predetermined region is 0, it means that a capacitor voltage value is maintained as a predetermined value in the corresponding section, and when the motor current value flowing in the motor of the compressor 30 is 0 at a particular vertex, it means that the capacitor voltage value at the vertex has the same value as that of an immediately previous capacitor voltage value.

The triac voltage calculator 94 may calculate a triac voltage value using the input voltage, the motor voltage, and the capacitor voltage value calculated by the capacitor voltage calculator 92. The triac voltage calculator 94 may subtract the motor voltage from the input voltage to obtain a value, and subtract the capacitor voltage value from the obtained value to calculate the triac voltage value. Namely, the triac voltage value may be calculated by Equation 4 derived from Equation 1.

Vtriac(k)=Vin(k)−Vm(k)−Vcap(k)  [Equation 4]

A graph including triac voltage values calculated by the triac voltage calculator 94 is illustrated in FIG. 2. As illustrated in FIG. 2, waveforms of the input voltage and the motor voltage detected through one or more sensors and the capacitor voltage calculated by the capacitor voltage calculator 92 are illustrated. The triac voltage values are calculated using the detected input voltage, the motor voltage, and the calculated capacitor voltage values. As illustrated, in the first region shown in FIG. 1, namely, in the section in which a current value flowing in the motor of the compressor 30 is not 0, the triac voltage value is 0. Meanwhile, in a section in which the current value flowing in the motor of the compressor 30 is 0, the triac voltage value is calculated by Equation 4.

Also, the microcomputer 90 may generate a gate driving signal of the triac 20 and transfer the generated gate driving signal to control a stroke of the compressor 30.

The input voltage detector 50 may detect an input voltage of the commercial power source 10. The input voltage detector 50 may check for a change in voltage.

The motor voltage detector 60 may detect a motor voltage applied to the motor of the compressor 30. The motor current detector 80 may detect a motor current flowing in the motor of the compressor 30. A stroke for controlling the compressor 30 may be calculated from the motor voltage detected by the motor voltage detector 60 and the motor current detected by the motor current detection unit 80. Also, the motor current detector 80 may be, for example, a current transformer (CT).

The zero voltage detector 70 may detect a zero voltage from the input voltage detected by the input voltage detector 50. The zero voltage detector 70 may check for a change in frequency.

Also, the apparatus for controlling a compressor may further include a switch (not shown) connected to the triac 20 that operates to connect the triac 20 to the motor of the compressor 30 or directly connects the commercial power source 10 to the motor of the compressor 30 according to a control signal. The switch (not shown) may be a protection relay to protect the triac 20.

In addition, the apparatus for controlling a compressor may further include a rectifier (not shown) that rectifies and/or smooths the power from the commercial power source 10 and supplies the same to the motor of the compressor 30.

In the case of the apparatus for controlling a compressor and the method for controlling a compressor according to embodiments, without using a voltage sensor to detect a capacitor voltage and a triac voltage, the capacitor voltage and the triac voltage may be calculated using an input voltage value of the commercial power source, a motor voltage value of the compressor motor, and a motor current value of the compressor motor. Thus, the calculation may be easily performed and an additional operational amplifier (OPAMP) or an extra sensor is not required to be used.

A method for controlling a compressor according to embodiments will be described in detail with reference to FIGS. 3 and 4.

In general, in a reciprocating compressor, a piston may move vertically by an application voltage according to a stroke reference value set by a user, and thus, a stroke is varied to regulate freezing capacity. The triac 20 may increase the stroke by lengthening a turn-on period of gate driving or reduce the stroke by shortening the turn-on period of gate driving according to a switching control signal transferred from the microcomputer 90.

In the method for controlling a compressor according to an embodiment, for example, an input voltage of a commercial power source, a motor voltage of the compressor motor, and a motor current of the compressor motor may be detected using, for example, a sensor or an operational amplifier (OPAMP), in step S10. In more detail, the motor voltage detector 60 and the motor current detector 80 may detect a voltage and a current applied to the motor of the compressor 30 and apply the same to the microcomputer 90.

Thereafter, a capacitor voltage of the capacitor connected to the compressor motor may be calculated using the detected input voltage, the motor voltage, and the motor current values, in step S20. When the detected motor current value is 0, the capacitor voltage may be calculated as a predetermined voltage value. Namely, while the detected motor current value is 0, there is no change in the capacitor voltage value. When the detection motor current value is not 0, a voltage value of the capacitor may be calculated by subtracting a corresponding motor voltage value from the detected input voltage value. That is, while the detected motor current value is not 0, the capacitor voltage value may be calculated from a difference between the input voltage and the motor voltage value. Thereafter, a triac voltage value of the triac operating the compressor motor may be calculated according to a gate driving signal by using the calculated capacitor voltage values, in step S30.

The microcomputer 90 may calculate a stroke of the compressor 30 using the voltage and the current detected by the motor voltage detector 60 and the motor current detector 80. Thereafter, the microcomputer 90 may compare the calculated stroke with a predetermined stroke command, and output a switching control signal for switching the triac 20 based on the comparison result.

When the stroke is smaller than the stroke command value, the microcomputer 90 may output a switching control signal for lengthening an ON period of the triac 20 to increase a voltage applied to the motor of the compressor 30. That is, when the calculated stroke is smaller than the stroke command value, the microcomputer 90 may change the calculated voltage value of the triac 20 in order to increase a firing angle of the switching control signal. Meanwhile, when the calculated stroke is greater than the stroke reference value, the microcomputer 90 may change the calculated voltage value in order to reduce the firing angle of the switching control signal.

In other words, the stroke may be calculated using the motor voltage and the motor current, and the calculated stroke may be compared with the stroke reference value to increase or decrease the firing angle of the triac, thus changing the calculated voltage value of the triac. Namely, the triac may be turned on during a predetermined turn-on time of the triac and generate a motor voltage corresponding to a desired stroke. Also, the triac may be maintained in the ON state during a predetermined connection time interval of the triac, and then turned off.

In this manner, the process of calculating a voltage value of the triac for controlling the compressor may include subtracting the motor voltage from the input voltage to obtain a value, and subtracting the capacitor voltage value calculated in step S20 from the obtained value. In this manner, in the method for controlling a compressor according to embodiments, the capacitor voltage value and the triac voltage value required for controlling a compressor may be calculated using the input voltage of the commercial power, the motor voltage of the compressor motor, and the motor current of the compressor motor, without using an extra sensor.

Also, in embodiments disclosed herein, the motor voltage, the calculated voltage value of the capacitor, and the voltage value of the triac may be monitored at predetermined time intervals, to determine whether there is an error in driving the compressor. Also, while monitoring the detected or calculated voltage values, when an error of the input voltage of the commercial power source applied to the compressor motor is detected, at least one of the voltages among the motor voltage, the capacitor voltage, and the triac voltage may be changed accordingly.

As described above, in the case of the apparatus for controlling a compressor and the method for controlling a compressor according to embodiments, a capacitor voltage and a triac voltage required for protecting a capacitor and a triac may be calculated using an input voltage of the commercial power source, a motor voltage of the compressor motor, and a motor current of the compressor motor without using a sensor. Thus, voltage values of the capacitor and the triac may be easily calculated and an additional operational amplifier (OPAMP) or an extra sensor is not required, reducing production costs.

Embodiments disclosed herein provide an apparatus for controlling a compressor capable of detecting (or calculating) a capacitor voltage and a triac voltage, which are required to protect a compressor in an abnormal state, such as, for example, an overload state, in controlling a compressor, using an input voltage of commercial power source, a motor voltage of a compressor motor, and a motor current of a compressor motor detected by a predetermined unit, without using a sensor.

Embodiments disclosed herein provide an apparatus for controlling a compressor that may include one or more capacitors connected to a compressor motor; a triac that operates the compressor motor according to a gate driving signal; and a microcomputer that generates the gate driving signal, and calculates voltage values of the capacitors and the triac using values of an input voltage of a commercial power source, a motor voltage of the compressor motor, and a motor current of the compressor motor.

The microcomputer may include a capacitor voltage calculation unit or calculator that calculates a voltage value of the capacitor, and when the motor current value is 0, the capacitor voltage calculation unit may calculate a predetermined capacitor voltage value. The microcomputer may include a capacitor voltage calculation unit that calculates a voltage value of the capacitor, and when the motor current value is not 0, the capacitor voltage calculation unit may calculate a value obtained by subtracting the motor voltage from the input voltage, as a voltage value of the capacitor.

The microcomputer may include a triac voltage calculation unit or calculator that calculates a triac voltage value using the input voltage, the motor voltage, and the capacitor voltage value. The triac voltage calculation unit may subtract the motor voltage from the input voltage, and subtract the capacitor voltage value from the resultant subtraction value to calculate the triac voltage value.

The apparatus may further include an input voltage detection unit or detector that detects an input voltage of the commercial power source; a motor voltage detection unit or detector that detects a motor voltage applied to the compressor motor, and a motor current detection unit or detector that detects a motor current flowing in the compressor motor. The apparatus may further include a zero voltage detection unit or detector that detects a zero voltage from the detected input voltage. The apparatus may further include a commercial power source that supplies power to the compressor motor, and a rectifying unit or rectifyier that rectifies and smooths the power provided from the commercial power source. The apparatus may additionally include a switching unit or switch connected to the triac and connecting the triac to the compressor motor or directly connecting the commercial power source to the compressor motor according to a control signal. The microcomputer may generate the control signal for controlling an operation of the switching unit and provide the generated control signal to the switching unit.

Embodiments disclosed herein provide a method for controlling a compressor that may include detecting an input voltage of a commercial power source, a motor voltage of a compressor motor, and a motor current of the compressor motor; calculating a voltage of a capacitor connected to the compressor motor using the input voltage, the motor voltage, and the motor current; calculating a voltage of a triac operating the compressor motor according to a gate driving signal using the calculated capacitor voltage; and controlling the compressor using the detected input voltage, the motor voltage, and the motor current, and the calculated voltage of the capacitor and the voltage of the triac.

In the calculating of the voltage of the capacitor, when the motor current value is 0, a predetermined voltage value may be calculated. Further, in the calculating of the voltage of the capacitor, when the motor current value is not 0, a value obtained by subtracting the motor voltage from the input voltage may be calculated. In the calculating of the voltage of the triac, a value may be obtained by subtracting the motor voltage from the input voltage, and the calculated voltage of the capacitor may be subtracted from the obtained value to calculate the voltage of the triac. The method may further include detecting whether the compressor has an error by monitoring the values of the motor voltage, the capacitor voltage and the triac voltage.

In the case of the apparatus and method for controlling a compressor according to embodiments, the capacitor voltage and the triac voltage required for protecting a compressor may be detected using an input voltage of a commercial power source, a motor voltage of the compressor motor, and the motor current of the compressor motor. Thus, the calculation may be easily performed, and an additional operational amplifier or an extra sensor to measure the capacitor voltage may not be required, reducing costs.

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 

What is claimed is:
 1. An apparatus for controlling a compressor, the apparatus comprising: one or more capacitors connected to a compressor motor; a triac that operates the compressor motor according to a gate driving signal; and a microcomputer that generates the gate driving signal, and calculates voltage values of the one or more capacitors and the triac using an input voltage of a commercial power source, a motor voltage of the compressor motor, and a motor current of the compressor motor.
 2. The apparatus of claim 1, wherein the microcomputer includes a capacitor voltage calculator that calculates voltage values of the capacitor, wherein when the motor current is 0, the capacitor voltage calculator calculates a predetermined capacitor voltage value.
 3. The apparatus of claim 1, wherein the microcomputer includes a capacitor voltage calculator that calculates voltage values of the capacitor, wherein when a value of the motor current is not 0, the capacitor voltage calculator calculates a value obtained by subtracting the motor voltage from the input voltage, as a voltage value of the capacitor.
 4. The apparatus of claim 2, wherein the microcomputer includes a triac voltage calculator that calculates triac voltage values using the input voltage, the motor voltage, and the capacitor voltage value.
 5. The apparatus of claim 4, wherein the triac voltage calculator subtracts a value of the motor voltage from a value of the input voltage, and subtracts the capacitor voltage value from the resultant subtraction value to calculate the triac voltage values.
 6. The apparatus of claim 1, further comprising: an input voltage detector that detects an input voltage of the commercial power source; a motor voltage detector that detects a motor voltage applied to the compressor motor; and a motor current detector that detects a motor current flowing in the compressor motor.
 7. The apparatus of claim 7, further comprising: a zero voltage detector that detects a zero voltage from the detected input voltage.
 8. The apparatus of claim 1, further comprising: a commercial power source that supplies power to the compressor motor; and a rectifyier that rectifies and smooths the power provided from the commercial power source.
 9. The apparatus of claim 1, further comprising: a switch connected to the triac, the switch connecting the triac to the compressor motor or directly connecting the commercial power source to the compressor motor according to a control signal.
 10. The apparatus of claim 9, wherein the microcomputer generates the control signal for controlling an operation of the switch and provides the generated control signal to the switch.
 11. The apparatus of claim 1, wherein the compressor comprises a reciprocating compressor.
 12. A method for controlling a compressor, the method comprising: detecting an input voltage of a commercial power source, a motor voltage of a compressor motor, and a motor current of the compressor motor; calculating a voltage of a capacitor connected to the compressor motor using the input voltage, the motor voltage, and the motor current; calculating a voltage of a triac operating the compressor motor according to a gate driving signal using the calculated capacitor voltage; and controlling the compressor using the detected input voltage, the motor voltage, and the motor current, and the calculated voltages of the capacitor and the triac.
 13. The method of claim 12, wherein in the calculating of the voltage of the capacitor, when the motor current is 0, a predetermined voltage is calculated.
 14. The method of claim 12, wherein in the calculating of the voltage of the capacitor, when the motor current is not 0, a voltage value obtained by subtracting the motor voltage from the input voltage is calculated.
 15. The method of claim 12, wherein in the calculating of the voltage of the triac, a value is obtained by subtracting the motor voltage from the input voltage, and the calculated voltage of the capacitor is subtracted from the obtained value to calculate the voltage of the triac.
 16. The method of claim 12, further comprising: detecting whether the compressor has an error by monitoring the motor voltage, the capacitor voltage, and the triac voltage.
 17. The method of claim 12, wherein the compressor comprises a reciprocating compressor. 